Two Blastomyces dermatitidis commercial immunodiffusion antigens, Meridian Diagnostics and Nolan-Scott Laboratories, and two B. dermatitidis yeast phase lysate antigens, T-58 and K-Le, prepared in our laboratory were utilized in an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in 61 serum specimens from dogs with blastomycosis. All antigens used in the ELISA were diluted to 50 ng of protein ml-1. Immunodiffusion (ID) tests were also performed on the sera using a Nolan-Scott ID antigen. Greater reactivity, based on the ELISA index value, was evidenced with the two yeast phase lysate antigens over the two commercial reagents in the ELISA. In addition the sensitivity of the ELISA with the T-58, K-Le and Meridian antigens was considerably greater than that of the ID test. The Nolan-Scott antigen, however, was able to detect more positive specimens when used in the ID procedure than in the ELISA. Therefore encouraging results were obtained with respect to the continued development and optimization of the ELISA using B. dermatitidis cell lysate antigens for the diagnosis of blastomycosis.